Deterministic Ferroelastic Domain Switching Using\nFerroelectric Bilayers

Abstract

Composition\ngradients, or dissimilar ferroelectric bilayers, demonstrate\ncolossal electromechanical figures of merit attributed to the motion\nof ferroelastic domain walls. Yet, mechanistic understanding of polarization\nswitching pathways that drive ferroelastic switching in these systems\nremains elusive. Here, the crucial roles of strain and electrostatic\nboundary conditions in ferroelectric bilayer systems are revealed,\nwhich underpin their ferroelastic switching dynamics. Using in situ\nelectrical biasing in the transmission electron microscope (TEM),\nthe motion of ferroelastic domain walls is investigated in a tetragonal\n(T) Pb­(Zr,Ti)­O₃ (PZT)/rhombohedral (R) PZT epitaxial bilayer\nsystem. Atomic resolution electron microscopy, in tandem with phase\nfield simulations, indicates that ferroelastic switching is triggered\nby predominant nucleation at the triple domain junctions located at\nthe interface between the T/R layers. Furthermore, this interfacial\nnucleation leads to systematic reversable reorientation of ferroelastic\ndomain walls. Deterministic ferroelastic domain switching, driven\nby the interfacial strain and electrostatic boundary conditions in\nthe ferroelectric bilayer, provides a viable pathway toward novel\ndesign of miniaturized energy-efficient electromechanical devices.